The Canon Speedlite 600 EX II-RT is a powerful, water-resistant external flash. With this flash, you can light a subject at a great distance, thanks to the 20-200mm zoom range and the guide number of 60. The body and hot shoe connection are water resistant. This means you can safely take the flash with you if there's a chance of rain. The head zooms automatically with the lens. You can set the sensor size, so the guide number is adjusted to the focal length. With the remote-controlled flash system, you can control 5 groups and 15 flashes. The recycle time of this flash is 0.1 to 5.5 seconds.